This application claims the priority of German Patent Application, Serial No. 101 51 243.0, filed Oct. 17, 2001, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference.
The present invention relates, in general, to a revolution counter.
European Pat. No. EP 0 658 745 B1 describes a revolution counter for ascertaining the number of revolution of a revolving shaft. The revolution counter has a base body and a rotary element which rotates about a rotation axis with respect to the base body and is securely fixed in the base body in axial and radial directions. Due to manufacturing, assembly and functional considerations, the rotation axis of the rotary element and the axis of revolution of the revolving shaft are spaced from one another so that mechanical forces and torque are transmitted from the revolving shaft via the rotary element to the base body. Damage to the support of the rotary element in the base body can thus be avoided only through provision of a compensating coupling or torque support.
It would therefore be desirable and advantageous to provide an improved revolution counter which obviates prior art shortcomings and which is simple in structure and yet reliable in operation, without requiring the provision of a compensating coupling or torque support.
According to one aspect of the present invention, a revolution counter includes a base body accommodating a sensor arrangement and a power supply device for providing electric energy to the sensor arrangement, a rotary element intended for connection to a revolving member and rotating relative to the base body about a rotation axis, a reference element intended for connection to the base body for providing a reference for the revolving element, a magnet arrangement disposed on the rotary element and so interacting with the power supply device that the sensor arrangement is supplied with energy during each revolution of the rotary element in at least three rotary positions of the rotary element regardless of a rotation speed of the rotary element to thereby allow the sensor arrangement to ascertain a rotary position of the rotary element, wherein the rotary element is positioned with respect to the base body either without connection to the base body, or held by the base body at three-dimensional play, to thereby prevent a transfer of mechanical forces from the rotary element onto the base body, when the rotary element is connected with the revolving member and the base body is connected with the reference member.
The present invention resolves prior art problems by loosely placing and thus floatingly supporting the rotary element with respect to the base body and using the revolving member for support of the rotary element, when the revolution counter is actually installed for use through connection to the revolving member. As a result, the need for a separate, substantially play-free support in the base body is thus eliminated.
According to another feature of the present invention, the power supply device may include at least one energy storage magnet, which is supported on the base body for rotation about a center axis, and a coil, whereby the energy storage magnet impulsively reverses about the center axis, when the rotary element has a rotation speed below a minimum value and reached a predetermined rotary position, to thereby induce in the coil an energy pulse for supply of energy to the sensor arrangement. In this way, the power supply to the sensor arrangement is ensured, even when the rotary element rotates slowly.
According to another feature of the present invention, the center axis may extends substantially vertical to the rotation axis. As a result, the power supply device operates especially reliable, when the rotation speed of the rotary element is below a minimum rotation speed.
According to another feature of the present invention, the energy storage magnet and the coil are magnetically coupled by a core which extends from the energy storage magnet in a direction beyond the coil to the magnet arrangement. In this way, the energy pulses, generated in the coil, have maximum energy, when the energy storage magnet is impulsively reversed. Moreover, the interconnection of the magnet arrangement with the coil is improved, when the rotation speed is above a minimum level so that the electric energy generated by the coil is increased also in this situation.
According to another feature of the present invention, the energy storage magnet may be mounted on an axle, which defines the center axis and is supported by a bearing member which is connected to the core. Thus, the gap between the energy storage magnet and the core can be adjusted in a particularly easy and precise manner, thereby further enhancing the energy content of generated energy (voltage) pulses.
According to another feature of the present invention, the core may extend beyond the coil to a position just shy above the magnet arrangement with respect to the rotation axis. In particular, when the magnet arrangement is axially magnetized, the magnetic connection between the magnet arrangement, on the one hand, and the coil and energy storage magnet, on the other hand, is especially good. As an alternative, it is also conceivable that the core end terminates next to the magnet arrangement with respect to the rotation axis, so that the gap between the magnet arrangement and the core can have narrower tolerance. In this case, the magnet arrangement may be selectively magnetized axially or radially.
According to another feature of the present invention, the rotary element may have a coupler for magnetically connecting diametrically opposite regions of the magnet arrangement. This configuration results in a further enhanced magnetic connection between the magnet arrangement and the core. A simplest design involves the provision of the coupler in the form of an iron disk which is connected to the magnet arrangement on the side facing away from the core.
In view of the floating support of the rotary element of a revolution counter according to the present invention, the rotary element can easily adjust to the configuration of a revolving member, e.g., a revolving shaft, before attachment and no mechanical forces can be transmitted from the rotary element to the base body after the rotary element is connected to the revolving member and the base body is secured to the reference element. The need for a play-free support of the rotary element is no longer required, and the arrangement of a compensating coupling or a torque support is no longer needed. Yet a revolution counter according to the present invention is reliable in operation.